Box Stock

Compression ratio formula, need a little help or info

B

BLACK DEATH

Member
I have a VC 460, their site says it’s a 10-1 engine when you assemble it stock.
When I put the info into an engine compression ratio calculator I get closer to 12-1, unless I am doing something wrong.
Anyone want to help me figure this compression ratio out?
92mm bore, 69mm stroke, 41cc head, .020 head gasket, head gasket bore is 92mm, zero deck & a flat top piston.
 
11.49 is what the wallace calculator gave .
No valve reliefs , absolute zero , or looks like zero ?
Thicker head gasket if you want 10-1
 
You have a link to that calculator?
This is the one I’ve been using and it gives me 12.15-1
http://www.csgnetwork.com/compcalc.html
No valve reliefs and zero deck, I checked.
I just want to ensure my current compression ratio is accurate, especially since I weld the chamber up for more compression.
Once cleaned up, it may be around a 32cc
 
No i just googled it .
Also added one cc for valve reliefs some didn't like zero .
41cc down to 32 is going to raise it .
 
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COMPRSSTION 460.jpg
 
Given the information you provided rounded off and using Pi to 2 decimals. Piston swept volume is 458.4 cc volume of head gasket is 3.32cc , cyl. head volume is 41cc Combustion chamber 41cc plus hd gasket 3,32 = 44.32 458.4/44.32 = 10.34 therefore 10.34:1 static compression
 
Kart43 said:
Given the information you provided rounded off and using Pi to 2 decimals. Piston swept volume is 458.4 cc volume of head gasket is 3.32cc , cyl. head volume is 41cc Combustion chamber 41cc plus hd gasket 3,32 = 44.32 458.4/44.32 = 10.34 therefore 10.34:1 static compression
Click to expand...
Total swept volume must include , the head and gasket volume as well .
458.4 +44.32=502.72 ÷44.32=11.34296
Odd that no calculations are the same .
 
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Funny guy😊 , who's right . Thats a good one .
I will stick with the 11.5 range .
There is a discrepency in al's gasket volume and kart 43 . .337 vs 3.32
Which will change the outcome . As will the swept volume vs total swept volume hand calculation.
If you want real technical , add in the space from top of piston too the top of the ring .
Or cc it.
 
I am not familiar with that engine at all, so take my advice with a grain of salt. What is wrong with a cr of around 11.5? Why do you want to reduce it? If a reduction is necessary why not increase combustion chamber volume by un-shrouding the valves and hopefully increasing flow?
 
The head gasket volume does not get included in the pistons swept volume when you have zero pop up The head gasket volume now becomes part of the combustion chamber.
 
We got it now I do hand math , Al I got doubting myself when looking at yourinitial calculations and then did my final step incorrectly. 11.34:1
 
Flattop, I was just asking as I’ve been getting all types of calculations. I just wanted to make sure which is correct as I’ve seen different numbers. I get close to 12-1 on one of the online calculators. I didn’t mean no disrespect towards you or anyone. 11.5-1 sounds good to me.
Chipg56, I’m going to weld up the head for more compression, I just want to make sure what I have now so when we get the final cc numbers on the welded head, I’ll know the compression ratio will be. I’m running VP 110 octane already.
kart43, it seems most of you guys say 11.3-1, I’ll take around the 11.5-1 ratio
 
I get it . Online calculators may round up or or the numbers inputed were off some didnt like zero . Three that hit within.20 is pretty close .
Same as a 460 is actually 458 cc by bore and stroke .
If you know the compression ratio you want too acheive you should be able to get close with them .
 
BLACK DEATH said:
Flattop, I was just asking as I’ve been getting all types of calculations. I just wanted to make sure which is correct as I’ve seen different numbers. I get close to 12-1 on one of the online calculators. I didn’t mean no disrespect towards you or anyone. 11.5-1 sounds good to me.
Chipg56, I’m going to weld up the head for more compression, I just want to make sure what I have now so when we get the final cc numbers on the welded head, I’ll know the compression ratio will be. I’m running VP 110 octane already.
kart43, it seems most of you guys say 11.3-1, I’ll take around the 11.5-1 ratio
Click to expand...
There is a big difference between 11.5 and 11.3 and I assure you the 11.3 is correct for the information available.
 
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